7A.20 Squeegee Application of Two-Part Adhesive

7A.20.1 The simplest way to apply the adhesive is by pouring the mixed adhesive on the substrate and spreading it with a 3/16" (5 mm) or 1/4" (6 mm) (maximum) saw-toothed squeegee. The same techniques that are outlined in the following are applicable to traditional base sheets, ply felts and modified bitumen sheets.

7A.20.2 Starting at the low edge of the roof, the mixed adhesive is poured onto the area where the sheet will be installed. The adhesive is spread along the roof in a width slightly wider than the sheet. The sheet is then rolled, scrolled or flopped into the adhesive. It must be firmly and uniformly set, without voids, into the adhesive. Brooming is recommended to assure embedment.

Repositioning or straightening of the sheet can be accomplished after it is completely laid out. Spreading of the adhesive is continued along the roof. Subsequent sheets are installed in the same  manner, however the adhesive is applied to the top side of the last 4" (102 mm) of the preceding sheet to form an end lap (6" [152 mm] for DynaLastic 180, DynaLastic 180 FR, DynaLastic 180 S, DynaLastic 250 and DynaLastic 250 FR).

7A.20.3 Subsequent courses are applied in the same manner as before with the adhesive being spread onto the lower course in the selvage edge area to seal the side laps.

7A.20.4 It is recommended that all modified bitumen sheets be unrolled, placed upside down and allowed to "relax" for approximately 15 minutes prior to starting the adhesive application. This will permit the sheet to lay flat and should eliminate the formation of creases and fish mouths.

7A.21 Spray Application of Two-Part Adhesive

7A.21.1 Spray application of MBR Bonding Cement is possible using a Binks "Hawk 4L" unit. However, the material must be handled with care or the mechanical equipment can become severely damaged.

7A.21.2 Pour a minimum of 3 gallons (11.4 liters) of solvent (paint thinner or mineral spirits) into a clean 5 gallon (18.9 liter) pail and set the pump into it. Connect the hoses, take the air cap off the gun, and with the atomizing air pressure turned off, pump solvent through the gun and back into the pail. This will clean the lines and assure that the hose pump and gun are working properly. This will also lubricate the hose, retarding the build-up of adhesive on the inside of the hose. When equipment setup is complete, adjust the atomizing air pressure to about 40 psi (277 kPa) and replace the air cap on the gun. Similar techniques should be followed for comparable equipment. Consult spray equipment manufacturer for recommendations on the use of this adhesive with their machine and guns.

7A.22 Adhesive Spraying

Using the same lay-up procedures prescribed in the squeegee application method, employ the following spray techniques. Place the pump on a freshly prepared pail of adhesive and purge the system of solvent, spraying into a waste pail. When the adhesive begins spraying, move to the application area and coat the substrate in a width and length slightly larger than the sheet being applied. The adhesive should be sprayed to provide full coverage of about 30 mils (0.8 mm) thickness. Once the area has been sprayed, the sheet may be rolled, scrolled or flopped into the bed of adhesive. The end laps must be sprayed to create a seal when the subsequent roll of roofing material is installed. The spray crew should continue to progressively spray more substrate while additional personnel are laying and positioning sheets. Freshly laid sheets should be shielded from the spraying operation to prevent over-spray. Over-spray will not adversely affect the performance of the roof, but may detract from the aesthetics of the system.

7A.22.1 Upon completion of laying the first course of material, the next course is laid in a similar manner. Adhesive must be sprayed on the selvage edge of the preceding sheet to seal the side lap. For mineral surface products, the working sheet can be used as the shield for the preceding sheet by laying it upside down on the preceding sheet aligned with the laying line. Then, when the spraying operation has moved away, the shielding sheet is flopped over into the bed of adhesive.

7A.22.2 Depending on the ambient weather conditions on the roof (temperature, sunshine, etc.), the spraying operation must be periodically interrupted to purge the spray equipment. This will prevent a build-up of partially cured material in the hoses, pumps or gun. It is recommended that after spraying 5 pails of adhesive, the following operation be performed. Remove the air cap, turn off the atomizing air, place the pump on a pail containing solvent (the same one used to originally purge the system), and cycle the solvent through the system until the equipment is cleared. The submerged sections of the pump should be cleaned at this time, also. The frequency of the procedure may be slightly extended on cool, cloudy days to every 6 pails.

7A.23 Two-Part Adhesive Clean Up

7A.23.1 Immediately upon completion of work, clean the mixing, pumping, and spraying equipment and other tools. The mixing equipment and tools are cleaned by wiping down with solvent-soaked rags. Protective clothing, safety glasses, and impervious gloves must be worn for this operation. Wipe down the outside of the pump thoroughly with "used" solvent.

7A.23.2 Place the pump in the used solvent, and with the air cap removed and the atomizing air pressure off, circulate solvent through the pump, hose and gun for a minimum of 5 minutes.

Note: Once the MBR Cement has set up, the solvent will no longer remove it.